Apparatus for producing electric oscillations



y 1930- A. MOL. NICOLSON 1,760,251

APPARATUS FORPRODUCING ELECTRIC OSCILLATIONS Filed Dec. 20, 1926 2 Sheets-Sheet 1 7 j 8 0c .6 7 L24 40/00 i /A V80,

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9 10 12 13 j 7. PRIM Movai 8 4c 1000 :llllll INVENTOR ALEXANDER McLEAN NICOLSON BY W flza 42 ATTORNEY y 1930- V A. MOL. Nl COLSON 1,760,251

APPARATUS FOR PRODUCING ELECTRIC OSCILLATIONS Filed Dec. 20, 1926 2 Sheets-Sheet 2 8 HlIl l- INVENTOR ALEXANDER Mt LEAN NICOLSON Patented May .27, 1939 warren sari:

ALEXANDER MCLEAN NICOLSGN, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGN- IVIENTS, TO FEDERAL TELEGRAPH COMPANY, A CORPGB-A'I'ION 01* CALIFORNIA APPARATUS FOR PRODUCING ELECTRIC QSCILLATIONS Application filed December 20, 1926. Serial No. 155,901.

T his invention relates to a method and apparatus for producing electric oscillations, and more particularly, to a method and means comprising a piezo-electric device for 5 producing sustained electrical oscillations of a desired frequency.

It is an object of this invention to provide a method and apparatus for shocking a piezoelectric crystal device having a natural vibration frequency substantially that desired, whereby the crystal may be set into vibration at the said natural frequency to produce trains of electrical oscillations of that frequency.

ft is a further object of this invention to provide a method and apparatus for shocking such a crystal device periodically, at such intervals that a new train of oscillations is excited before the previous train has died away, whereby, in efiect, sustained oscillations are produced by the vibration of said crystal device.

It is still a further object of this invention to provide a method and apparatus of the class described which is self-sustaining in operation, that is, one in which a portion of the energy of the electrical oscillations, amplified if necessary or desired, is converted into mechanical force and applied to the piezo-electric device to administer shocks thereto, to

keep the system in operation.

Still other objects of this invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention, are set forth with particularity in the appended claims. My invention, itself, however, both as to its underlying principles and its practical embodiments, will best be understood by referring tothe specification and accompanying drawing in which,

Fig. 1 shows a simplified form of my invention,

Fig. 2 shows a similar arrangement in which additional stages of amplification are provided,

Fig. 3 shows a slightly different form of my invention,

Fig. 4 shows a still difierent form, in which a portion of the amplified energy output is converted into mechanical shocks for vibrating the crystal,

Fig. 5 shows still a different form of my invention.

In accordance with my invention, I select a piezo-electric crystal device, which may be a crystal of quartz, tourmaline, or other mineral crystal ground to the desired size and shape, or a crystal grown from solution such as Rochelle salt, or in a composite piezo-electric device, which may be formed by binding crystals together in an elastic matrix, or by casting fluid piezoelectrically active material in a mould, or by orienting crystals in a matrix by using seed crystals during solidification, or by applying internal electrodes, or by other suitable means.

In any event, the piezoelectric device is chosen and arranged to be resonant at the frequency of electric oscillations desired or at some fraction thereof, such as one'half, one'third, etc., whereby shocks administered to the crystal device cause it to vibrate at its own natural frequency and which vibration causes generation of trains of electric oscillations at said frequency and harmonics there- It will be understood that if a single shockv is administered, the crystal will set into-vibration but after a time, vibration will cease, due to expenditure of the energy imparted in overcoming internal friction and the like; and likewise, production of electric oscillations will cease. If, however, a second shock is administered to the crystal before it has ceased to vibrate in response to the first shock, a new train of vibrations will be set up and a new train of electric oscillations produced.

In the carrying out of my invent-ion, 1 provide a crystal device as described above, and also some means for imparting shocks thereto such for example, asa mechanical or electrical vibrator or tone source, or, in short, any device capable of periodically setting the crystal into mechanical vibration. Electrodes are provided on the crystal for withdrawing the charge produced by vibrations thereof, and preferably the charges so with drawn are impressed upon the input circuit of a thermionic amplifying device, or upon 9, and an anode 10.

a plurality of the same connected in cascade for the purpose of amplifying the oscillations to any extent desired.

A certain proportion of the amplified energy may be diverted from the load circuit and converted into a mechanical force which may be made to react upon the crystal to set it into vibration or to sustain vibrations already taking place.

Referring now more particularly to Fig. 1, 1 designates a piezoelectric crystal device herein shown diagrammatically. It is to be understood that as already stated, this may be a crystal of quartz, tourmaline, or other mineral, or grown crystal such as Rochelle salt, or a composite crystal of the sort described. above, The crystal. device is preterably provided with mounting plates 2 and 3 at opposite ends and with electrodes i and 5 associated with the crystal device in any desired manner for the purpose of collecting the charge generated by the crystal in vibra tion. While the electrodes are herein shown diagrammatically as applied on opposite sides, it will be understood that any suitable arrangement may be used such as an external equatorial electrode and an internal electrode if desired.

A suitable prime mover 6, herein diagrammatically shown, may be provided mounted upon a plate 8 and adapted to shock the crystal device mechanically. The prime mover 6, for example, may be a tuning "fork of the proper or adjustable frequency, ar-

ranged with the necessary batteries and coils and contacts to maintain itself in. vibration at the desired rate.

The vibrations are transmitted to plate 3 and through it to the crystal. device 1, causing the crystal to vibrate at its own natural frequency, producing a train of electrical oscillations. If the crystal damping is high and the impulses provided by the prime mover 6 are sufiiciently far apart, one train of oscillations will die away before the eX- citation of an additional train.

If it is desired to produce sustained oscillations, the frequency of the prime mover and frequency of thecrystal device will be so chosen that the mechanical shocks administered to the crystal device recur at such intervals that the train of electrical oscillations set up by the first shock is still in existence when the succeeding shock is administered to the crystal.

The charges generated upon the electrodes 4 and 5, may be impressed upon and control the input circuit of a thermionic amplifier 7 of the usual type, having a cathode 8 energized by suitable source of energy, such as battery 8, a control electrode such s grid A. suitable source oi potential for maintaining the anode 10 positive w1th respect to cathode 8, is provided, such as battery 11.

A choke 12 is also provided for the purpose of preventing the oscillations bypassing the alternating current load 13. Additional stages of amplification may be provided to increase the power of the alternating current to any desired value as shown by way of example in Fig. 2, wherein the thermionic amplifier 7 instead of being coupled directly to the load, is connected to the input circuit of an additional thermionic amplifier 1'? through the primary 15 of a transformer having its secondary 16 connected between the cathode 18 and grid 19 of thermionic amplifier 17, the output of which is coupled to the input circuit of a third thermionic amplifier 24 by means of primary 22 of transformer connected in the output circuit of amplifier 17 and having its secondary '23 connected between cathode 25 and grid 26 of amplifier 9A. The output of this amplifier may be supplied to the load as before.

thiitable sources of potential, such as batteries 21 and 28 are provided for maintaining the plates of the respective amplifiers positive, but it will be understood that this is merely by way of example, and that common batteries or different types of coupling may be used as is known in the art.

Referring now to Fig. 3, there is shown a iled arrangement in which the prime mo *er 6 instead of being directly associated ith the rystal is out of contact therewith and the vibrations are impressed upon the surrounding medium such as the atmosphere, and picked up by a receiving device mounted upon or associated'with the crystal, such acoustic diaphragm 30. The prime mover, in this instance may be a tone source, such as a phonograph emitting a continuous tone of desired frequency or an electrical 0scillator operating a loud speaker producing a tone of the desired frequency.

P ferring now to Fig. 4, I have shown a modified arrangen'ient inwhich a portion of the amplified energy output from a thermionic amplifier, is converted into mechanical motion or stress and applied to the crystal to sustain the operation of the system. In

this instance, the crystal device 1, provided with electrodes l and 5, is mounted upon or mechanically associated with a second crystal device provided, iitdesired, with mounting plates 36 and 37. The association between the crystal devicesmay be any association that suffices to convey mechanical vibrations from the one to the other.

The charge generated upon the crystal de vice i, w ion it is struck, for example, is impressed upon the control circuit of thermionic amplifier a0 having cathode 4-1 and control elect-rod 4:2 and an anode 43. A condenser i l of suitable value may be provided, connected between anode 43 and cathode 41; and

coil is likewise provided, having one terminal connected to anode 4:3 and through a suitable source of anode potential to cathode 4E1. Electrodes 38 and 39 of the crystal device 35, are connected respectively to cathode 41 and to a variable point 46.

The operation of this system, it is believed, will be readily understood from what has already been stated. If a shock is impressed upon the crystal device 1, a train of electrical oscillations will be generated and amplified by amplifier 40. The amplified oscillations or the desired proportion thereof, are impressed upon the crystal device 85, causing it to vibrate mechanically, and the mechanical vibrations are conveyed, by reason of the association of crystal device 1, to the said crystal to keep it vibrating and thereby generatin electrical oscillations.

y proper control of the natural frequen cies of crystal devices 1 and 35 and the mechanical coupling between them. a highly stable system for generating electrical oscillations of the desired frequency may be provided. The alternating current may be supplied to a load by means of coil 48 coupled to the coil 45.

Referring now to Fig. 5, there is provided a modified arrangement, comprising crystal device 55, having mounting plates 56 and 5'? and suitable electrodes 58 and 59. The lower mounting plateb? may be provided with an extension 60, forming an armature and contact adapted normally to rest upon a fixed contact 61 and thereby completing a circuit 'hrough suitable source of energy 63, such as a battery and lifting coil or solenoid or electromagnet 62 adapted to raise the arm off contact 61, and through the arm itself to the said contact.

-t will be understood that as soon as the circuit of source 63 is completed, the coil 62 will be energized to lift arm 60 from contact 61,

and upon the breaking of the contact at 61, the arm will fall back, whereupon contact will again be made, so that arm 60 is continually vibrated, thereby vibrating the crystal device 55 and generating trains of electrical oscillations which may be amplified as before.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will I be understood by those skilled in the art.

I claim: 7

1. In a system for generating alternating current of a predetermined frequency the combination of, a piezo electric crystal having a fundamental frequency corresponding to said predetermined frequency, a source of mechanical vibrations disposed adjacent to a face of said piezo electric crystal, a vacuum tube having input and output circuits, said piezo electric crystal being associated with the input circuit of said vacuum tube, said source of mechanical vibrations being connected to the output circuit of said vacuum tube whereby it is maintained in operation by energy received from said circuit.

2. In a'system for generating high frequency oscillations of a predetermined frequency the combinationof, a vacuum tube having input and output circuits coupled together, a piezo electric device associated with said circuits, a source of constant frequency mechanical vibrations adjacent to said piezo electric crystal said source being associated with said circuits for deriving its driving energy therefrom.

3. In a system for generating high frequency oscillations of a constant predetermined frequency the combination of, a vacuum tube having grid, filament and plate electrodes, an inductance connected to the plate electrode of said vacuum tube, a piezo electric crystal connected to said grid and filament electrodes, and a source of mechanical vibrations adjacent to a face of said piezo electric crystal, said source being connected to said vacuum tube for deriving its driving energy therefrom.

4. A system f r generating high frequency oscillations of a predetermined frequency comprising in combination, a thermionic electron tube having grid, filament and plate electrodes, a source of plate current supply, an inductance connected to said plate electrode and said source of current supply, a piezo electric crystal connected to said grid electrode and to said filament electrode, and a source of mechanical vibrations disposed adjacent to said piezo electric crystal for communicating mechanical vibrations thereto, said source of mechanical vibrations com prising a piezo electric crystal.

5. In a device for generating an alternating current of constant predetermined frequency the combination of, a thermionic electron tube, an inductance connected to said electron tube, a piezo electric crystal connected to said inductance and said electron tube, a second piezo electric crystal disposed adjacent to said first piezo electric crystal, connections between said second piezo electric crystal and said electron tube for causing said second piezo electric crystal to vibrate mechanically and thereby periodically impart mechanical shocks to said first mentioned piezo electric crystal.

6. In a device for generating an alternating current of constant predetermined frequency the combination of, a thermionic electron tube having input and output circuits, an inductance included in said output circuit, a piezo electric crystal having a fundamental frequency substantially equal to the predetermined frequency connected to said induc-' tance and the input circuit of said electron tube, a second piezo electric crystal disposed adjacent to said first named piezo electric crystal, connections between said electron tube and said second piezo electric crystal for diverting a partof the enery from the electron tube circuits to said second piezo electric crystal and causing said second piezo electric crystal to periodically mechanically shock the first piezo electric crystal.

7 In-a system for generating high frequency oscillations of a predetermined frequency, in combination, a thermionic electron tube having grid, cathode and plate electrodes, a source of plate current supply, an inductance connected to said plate electrode and to said source of plate current supply, a piezo-electric crystal connected to said inductan e and to said cathode electrode, and a second piezo-electric crystal connected to said cathode electrode and to said grid electrode, said first and second piezo-electric crystals being mechanically coupled together.

8. In a system for generating alternating current of a predetermined frequency, in combination, a piezo-electric crystal having a fundamental frequency corresponding to said predetermined frequency, a thermionic electron tubehaving grid, cathode and plate electrodes, an inductance connected to the plate electrode of said thermionic tube, said piezoelectric crystal being connected to said inductance and to said cathode electrode, a second piezo-electric crystal disposed adjacent said first mentioned piezo-electric crystal and electrically connected to said grid and cathode electrodes, and means for mechanically coupling said first and second piezo-electric crystals together.

In testimony whereof I hereunto afiix my signature. 7

ALEXANDER McLEAN llICQLSOll, 

